This invention relates to an industrial robot assembly. More particularly, this invention relates to a robot assembly having two relatively rotatable arm members coupled to one another and further having electric motors with associated transmissions for driving the arm members about rotation axes.
U.S. Pat. No. 4,348,142 discloses in FIG. 1 two arm members coupled to one another by a rotary joint, the arm members being relatively rotatable in the same horizontal plane. For driving such a pair of arm members about a rotary joint, electric motors with gear type transmissions are frequently integrated into the joint, as disclosed in German Patent Document (Auslegeschrift) No. 11 48 721. By arranging the electric motors at the rotary joints, very fast and precise movements are obtainable. However, moments of inertia are generally increased inasmuch as the drive motors are located at the tips of the arm members, i.e., at points located at maximum distances from a primary axis of rotation.
An object of the present invention is to provide an improved robot assembly of the above-described type.
Another, more particular, object of the present invention is to provide such a robot assembly having a fast and precise drive for each of the individual arm members and simultaneously having reduced moments of inertia.